Heat-treating-furnace roll and method of heat-treating metal strip therewith

ABSTRACT

Roll of the invention includes a roll body of metal and a sleeve, made up of fused silica particles sinter bonded with colloidal silica or cement, or a mixture of fused silica particles and particles of other oxides sinter bonded with colloidal silica or cement, or sinter bonded fireclay granules, fixedly surrounding the roll body. Method of the invention consists of the steps of supporting strip which is being heattreating at a temperature above 1000*F by a surface consisting of sintered fused silica particles, sintered fused silica mixed with other oxide particles, or sintered fireclay granules to inhibit formation of accretions on the supporting surface.

United States Patent 1191 Snow Aug. 7, 1973 HEAT-TREATING-FURNACE ROLLAND 2,772,872 12/1956 Ornitz 263/6 0 METHO OF HEAT TREATING METAL3,456,931 7/1969 Ermenc et al 263/6 C 3,511,482 5/1970 Haite 263/6 CSTRIP THEREWlTl-l Roland 8. Snow, Mount Lebanon Twsp., Allegheny County,Pa.

Filed: Aug. 18, 1971 Appl. No.: 172,947

Related U.S. Application Data Continuation-impart of Ser. No. 113,183,Feb. 8, 1971, abandoned.

lnventor:

U.S. Cl 432/8, 148/16, 432/246, 193/37 1m. Cl. .f. F26b 9/00 Field ofSearch 263/6 C, 6 R

References Cited UNITED STATES PATENTS 11/1929 Morton 263/6 C PrimaryExaminer-John J. Camby Assistant Examiner-Henry C. Yuen Attorney-DonaldS. Ferito [57] ABSTRACT Roll of the invention includes a roll body ofmetal and a sleeve, made up of fused silica particles sinter bonded withcolloidal silica or cement, or a mixture of fused silica particles andparticles of other oxides sinter bonded with colloidal silica or cement,or sinter bonded fireclay granules, fixedly surrounding the roll body.Method of the invention consists of the steps of supporting strip whichis being heat-treating at a temperature above 1000F by a surfaceconsisting-of sintered fused silica particles, sintered fused silicamixed with other oxide particles, or sintered fireclay granules toinhibit formation of accretions on the supporting surface.

12 Claims, 2 Drawing Figures PATENIEB AUG 7 W3 Ubm INVENTOR.

ROLAND B. SNOW By Attorney HEAT-TREATING-FURNACE ROLL AND METHOD OFHEAT-TREATING METAL STRIP THEREWITH This application is acontinuation-in-part of my copending application Ser. No. l l3,l83 filedFeb. 8, 1971, now abandoned. The present invention relates generally toheat-treating-furnace rolls and a method of heat-treating metal strip atrelatively high temperatures in which the strip is supported by therolls of the invention.

More particularly, particularly, the invention relates to furnaceconveyor rolls around which metal strip is passed and advanced throughcontinuous heating furnaces, such as annealing furnaces, to be heated torelatively high temperatures therein.

BACKGROUND OF THE INVENTION Conveyor rolls used in continuous stripannealing furnaces prior to my invention tended to collect accretions ofmaterial from the strip which dented or otherwise marred subsequentstrip passing over or around the rolls. The problem was particularlyacute in the treatment of silicon steels and other steels requiringrelatively high annealing temperatures, for example, tem peratures above1000F to temperatures in excess of 1600F. Such accretion formation iscomplex and is influenced by the tension of the strip passing around therolls, the composition of the strip, and the composition and temperatureof the furnace atmosphere as well as the character of the roll surface.It is to the latter element to which the roll and method of my inventionare particularly directed. I

Prior to my invention, refractory inserts such as silicon carbide wereused in furnace conveyor elements in such a way that the refractoryinserts supported the strip passing through the furnace. U. S. Pat. No.1,951,766 discloses furnace conveyor elements provided with refractoryelements for supporting the work passing through the furnace. While nooxide coating forms on silicon carbide inserts and rolls providedtherewith are satisfactory for annealing sheets, it was found that incontinuous strip annealing furnaces where the strip wraps around therolls under tension,

and especially in annealing silicon steel strip, accretions formed onthe silicon carbide inserts.- Furthermore, the provision andinstallation of the refractory inserts entailed substantial labor andexpense.

Another device tried for preventing accretions on strip supportingsurfaces during high temperature annealing was to provide a roll havinga removable carbon sleeve. U. S. Pat. No. 2,603,578 teaches a method ofheat-treating silicon steel including the use of rolls faced with eithergraphite or amorphous carbon. Such rolls were not satisfactory for usein all atmospheres or in the higher ranges of strip tension. 1

U. S. Pat. No. 2,778,872 teaches the use of rollsleeves made essentiallyof baked graphite particles and a binder. Although the carbonroll-sleeves were moderately successful, difficulty was experiencedresulting from uneven oxidation of the carbon sleeve. This causedhard-spots" on the roll which indented strip subsequently passing overthe roll. When this happened, the rolls had to be removed and theroll-sleeves re-dressed. A further disadvantage with rolls having carbonsleeves was the fact that such rolls could not be removed from thefurnace without cooling. If the rolls were removed at elevatedtemperatures, the sleeves would burn in the air.

Accordingly, it is the primary object of my invention to provide aheat-treating-furnace roll made up of a metal roll body and a sleeve ofa non-oxidizing material, such as sinter bonded fused silica tines,fused silica particles mixed with particles of other oxides sinterbonded with colloidal silica or cement, or sinter bonded fireclaygranules, surrounding the roll body, and the method of using such rollsduring high temperature treatment of metal strip, such as silicon strip.

It is a more specialized object of my invention to provide a roll as setforth in the above object having a sleeve made of fused silica finesthat have been sinter bonded with colloidal silica or cement binderresulting in a sleeve which will have a minimum degree of expansion orcontraction when subjected to changes of temperature.

Another more specialized object of my invention is to provide aheat-treating-furnace roll having a metal body and sleeve of anon-oxidizing material made of fused silica fines mixed with 0.5 to 20.0percent of other oxides sinter bonded with colloidal silica or cementsurrounding the metal roll body.

A further specialized object of my invention is to provide a roll forheat-treating metal strip at relatively high temperatures which roll isformed with a roll body and a sleeve surrounding the body made ofgranular fireclay that is sinter bonded with cement or other cold setbinders.

These and other objects will become more apparent after referring to thefollowing specification and attached drawing, in which:

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a front elevational viewpartly in section of a roll of the invention; and

FIG. 2 is an end view of the roll of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring more particularly tothe drawing, reference numeral 2 indicates generally a roll constructedin accordance with the invention. Roll 2 includes a metal hollow barrelroll body 8 having a porous ceramic sleeve 6 rigidly disposedtherearound. A preferred ceramic sleeve is generally composed of crushedfragments of SiO, glass which are mixed with colloidal silica thenformed into a roll sleeve and fired, preferably to approximately l800F,to produce a sinter bonded silica glass sleeve that resists metalabrasion from the strip that passes over the sleeve.

The sleeve 6 is preferably molded from silica glass fines with acolloidal silica or cement binder and then baked to provide a sinterbond of good strength. The fines are prepared by fusing quartz (SiO,)fragments to form a glass; the glass is then quenched and pulverized.The pulverized glass is then molded into the shape and size of sleeve 6with a colloidal silica or cement binder and then sinter baked toprovide a porous sleeve having good strength. The sleeve 6 thus formedhas excellent spalling resistance and may be inserted into or removedfrom a hot furnace without damage. The silica sleeve 6 has a low thermalconductivity as compared to silicon carbide inserts or carbon facing orcarbon sleeves used prior to my invention, and thus the fused silicasleeve 6 of the invention will transmit less heat to the roll body; thisprovides for a more stable roll assembly. The bonded silica fines arerelatively inexpensive and provide an appreciable cost savings. Thefused silica sleeve 6 does not have to be taken from the heat-treatingfurnace periodically to restore a crown thereon. In addition, attemperatures approaching 1800F, the surface of the silica glass sleeve 6will clevitrify and under these conditions silica glass roll-sleevescould be used in vertical heat-treating furnaces such as is shown inFIG. 1 of US. Pat. No. 2,603,578.

The sintered silica-glass composition of sleeve 6 has a bulk density ofapproximately llto I20 lbs/cu. ft. which is substantially a maximum forslip-cast material. The low thermal conductivity of this material (5.4BTU/in./hr./sq. ft. per F) provides for a heat savings in the furnacebecause less heat is transferred to the steel center portion of theroll. This value will vary if there is a change in the bulk density ofthe fixed roll sleeve. The sintered silica-glass composition has a lowrate of thermal expansion (0.3 X from 0 to 1800F) which is importantbecause it permits hot roll changes without cracking the ceramic sleeveand if there is some metal pick-up, the metal has so much greatercontraction on cooling than the sintered silica-glass sleeve that themetal pick-up will pull loose from the sleeve on cooling to roomtemperature or by variation of temperature during the furnace cycle. Anysuch metal pick-up is in the form of elongated 1/16 to H2 inch depositsand such pick-up would not form a continuous layer around the sleeve.While it is preferred that the thermal expansion be approximately 0.3 X10or less, it may be as high as 0.5 X 10'.

The sintered silica roll sleeves of the invention are more easilyresurfaced than sleeves of other materials and in the event that thereis some pick-up of metal or iron oxide that does not come loose oncooling down, the sintered silica-glass sleeve is easily reground; inmany cases even fine sand paper held in ones hand can be used to removesuch metal pick-up if it occurs.

At a temperature of [900 to I950F in a high water vapor atmosphere themetal pick-up has been removed in normal operations without cooling downof the furnace by the fluxing reaction between the silica roll and F e0formed by the oxidation of the iron in the pick-up. The liquid formed isrelatively fluid and the liquid oxide smears over the surface while theroll is turning and the oxide may even enter the pore spaces between thesintered silica particles. With other ceramic oxides that might be usedfor roll sleeves such as 100 percent alumina (A1,0,) this iron oxidereaction product would be a solid and a build-up could continue.However, a small amount of A1,0 in the pores of the sleeve or the rollbody may aid in the removal of this pick-up because limited amounts ofA1 0 lower the temperature at which the reaction between FeO and silicabecomes liquid.

Particles of other oxides such as fireclay CaO, MgO, Al,O ZrSiO and/orCr,O can be added to fused silicaglass in amounts of between 0.5 topercent without greatly affecting the favorable thermal expansion,conductivity, or spalling resistance of the similar bonded silicasleeve. Each of these oxides or combinations will be limited by theireffect on the thermal properties of the final body. Clay such ascalcined kaolin (A1,Si,0,) can be added in the greatest amount. It isalso possible to change the chemical characteristics of the roll surfaceby partially or completely impregnating the pores in the surface of thesilica sleeve with a substance which breaks down upon heating to depositchemical impurities in the pore spaces. After heating to 800F anychromic acid CrO H O which may enter the pores is converted to CrzOOther chemical substances such as aluminum chloride might be used tochange the surface chemistry of the roll without changing the generalcharacteristics of the sinter bonded silica glass particles in the rollsleeve.

If desired, an alternate composition can be used for forming sleeve 6.This composition may be granular fireclay that is sinter bonded withcement or other cold set binders.

The roll body 8 includes two tapered shaft ends 10. A drive ring 12 iscircumferentially disposed around each end of the roll body 8 and aclosure plate 14 is disposed at each end of the roll body. The shaftends 10 are each filled with insulating material 16. The roll body 8,the shaft ends 10, the drive rings 12 and the closure plates 14 may bemade of any suitable ferrous or nonferrous high temperature alloy suchas is ordinarily used in the manufacture of furnace conveyor elements.

The roll body 8 is formed with axially spaced circumferentialprojections or lands 18 forming bearings for sleeve 6. No venting of theroll body 8 is necessary since the sleeve 6 is sufficiently porous dueto the sinter bonding of the silica fines, mixture of silica fines andother oxides, or the granular fireclay during manufacture of the sleeve.The shaft ends 10 are provided with cylindrical portions 22 fittingwithin the ends of the roll body 8, tapered portions 24, and cylindricalend portions 26 and 28 of relatively great and relatively smalldiameter, respectively. The roll may be mounted for rotation in aheat-treating furnace in a conventional manner.

The ends of the roll body 8 may be welded to the shaft ends 10 by welds30 and the closure plates 14 may be welded to the shaft ends 10 by welds32. The drive rings 12 may be welded to the roll body 8 by welds 34, butone of the drive rings is not installed and welded to the barrel untilafter the sleeve 6 has been put in place on the roll body 8. Each of thedrive rings 12 has a series of circumferentially spaced radially andaxially extending projections 36 each of which enters a slot 38 providedtherefor in one of the ends of the sleeve 6 thus locking the sleeve tothe roll body 8so that the roll and sleeve function as a single unit.The slots 38 may be molded into the sleeve 6 at the time of itsformation or may be drilled after the piece has been molded and baked. 8so The sintered sleeve 6 constitutes the work engaging portion of theroll and its outer cylindrical surface 40 supports the strip as ittravels through the furnace.

Although I have described but three embodiments of my invention, otheradaptations and modifications may be made without departing from thescope of the following claims. I

I claim:

1. In the heat treatment of metal strip such as silicon steel strip inwhich said strip is heated to a temperature above l000F, the improvementtherewith of supporting said strip during the heat treatment by asurface made up of one of the group consisting of sinter bonded fusedsilica; sinter bonded fused silica having a content of up to 20 percentof at least one of the group consisting of fireclay, CaO, MgO, A1 0ZrSiO and G 0 and granular fireclay sinter bonded with a cold set binderto inhibit formation of accretions on said supporting surface.

2. The heat treatment of metal strip according to claim 1 in which saidstrip is supported during the heat treatment by a surface consisting ofsinter bonded fused silica.

3. The heat treatment of metal strip according to claim 1 in which saidstrip is supported during the heat treatment by a surface consisting ofsinter bonded fused silica having a content of up to 20 percent of atleast one of the group consisting of fireclay, CaO, MgO, Al O ZrSiO andCr O 4. The heat treatment of metal strip according to claim 1 in whichsaid strip is supported during the heat treatment by a surfaceconsisting of granular fireclay sinter bonded with a cold set binder.

5. A roll for supporting objects at elevated temperatures comprising aroll body, porous sleeve surrounding said roll body, said sleeve beingcomposed of one of the group consisting of sinter bonded fused silica;sinter bonded fused silica having a content of up to 20 percent of atleast one of the group consisting of fireclay, CaD, MgO, A1 ZrSiO and CrO 6. A roll according to claim 5 in which said sleeve has a maximumthermal coefficient of expansion from 0 to 1800F of approximately 0.5 X

' 7. A roll according to claim 5 in which said sleeve has a maximumthermal coefficient of expansion from 0 to 1800F of approximately 0.3 X10*.

8. A roll according to claim 5 in which said sleeve consistssubstantially of fused silica fines sinter bonded with a colloidalsilica binder.

9. A roll according to claim 5 in which said sleeve consistssubstantially of fused silica fines sinter bonded with a cement binder.

10. A roll according to claim 5 in which said sleeve consistssubstantially of a mixture of fused silica fines and up to 20 percent ofat least one of the group consisting of fireclay, CaO, MgO, A1 0 ZrSiOand Cr O said mixture being sinter bonded with a colloidal silicabinder.

11. A roll according to claim 5 in which said sleeve consistssubstantially of a mixture of fused silica fines and up to 20 percent ofat least one of the group consisting of fireclay, CaO, MgO, A1 0 ZrSiOand Cr O said mixture being sinter bonded with a cement binder.

12. A roll for supporting objects at elevated temperatures comprising aroll body, a porous sleeve surrounding said roll body, said sleeve beingcomposed substantially of granular fireclay sinter bonded with a coldset binder.

I UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 751195 Dated August 7 1973 Inventor(s) Roland SHOW It is certified thaterror appears in the above-identified patent and that said LettersPatent are hereby corrected as shown below:

Column 1, line 10, cancel "particularly,", second occurrence Column 2,line 19, after "and" insert a Column 3, line 10, "llOto" should read 110to Column 4, line 46, "850" should read 8 so line 50, after"baked."cancel "8 so". Column 5, claim 5, line 18, after "body," inserta line 23, "CaD" should read CaO Signed and: sealed this 12th dayofFebruary 1974.

(SEAL) Attest:

EDWARD M.FLETCHE R,JR. MARSHALL Attestl g Office! a Commissioner ofPatents FORM P'o-1o5o (10-69) USCOMWDC sowbpw i U.$. GOVERNMENTI'RINTING OFFICE "OI O-JOG-SSI,

2. The heat treatment of metal strip according to claim 1 in which said strip is supported during the heat treatment by a surface consisting of sinter bonded fused silica.
 3. The heat treatment of metal strip according to claim 1 in which said strip is supported during the heat treatment by a surface consisting of sinter bonded fused silica having a content of up to 20 percent of at least one of the group consisting of fireclay, CaO, MgO, Al2O3, ZrSiO4, and Cr2O3.
 4. The heat treatment of metal strip according to claim 1 in which said strip is supported during the heat treaTment by a surface consisting of granular fireclay sinter bonded with a cold set binder.
 5. A roll for supporting objects at elevated temperatures comprising a roll body, porous sleeve surrounding said roll body, said sleeve being composed of one of the group consisting of sinter bonded fused silica; sinter bonded fused silica having a content of up to 20 percent of at least one of the group consisting of fireclay, CaD, MgO, A12O3, ZrSiO4, and Cr2O3.
 6. A roll according to claim 5 in which said sleeve has a maximum thermal coefficient of expansion from 0* to 1800*F of approximately 0.5 X 10
 6. 7. A roll according to claim 5 in which said sleeve has a maximum thermal coefficient of expansion from 0* to 1800*F of approximately 0.3 X 10
 6. 8. A roll according to claim 5 in which said sleeve consists substantially of fused silica fines sinter bonded with a colloidal silica binder.
 9. A roll according to claim 5 in which said sleeve consists substantially of fused silica fines sinter bonded with a cement binder.
 10. A roll according to claim 5 in which said sleeve consists substantially of a mixture of fused silica fines and up to 20 percent of at least one of the group consisting of fireclay, CaO, MgO, A12O3, ZrSiO4, and Cr2O3, said mixture being sinter bonded with a colloidal silica binder.
 11. A roll according to claim 5 in which said sleeve consists substantially of a mixture of fused silica fines and up to 20 percent of at least one of the group consisting of fireclay, CaO, MgO, A1203, ZrSiO4, and Cr2O3, said mixture being sinter bonded with a cement binder.
 12. A roll for supporting objects at elevated temperatures comprising a roll body, a porous sleeve surrounding said roll body, said sleeve being composed substantially of granular fireclay sinter bonded with a cold set binder. 